Buck topology allowing step-up and polarity change

ABSTRACT

A buck topology that provides voltage step up and polarity change is disclosed. In one embodiment a converter includes an input for receiving an input voltage, a switching circuit coupled to the input for receiving a first driving signal, a floating voltage source coupled to the switching circuit for producing an offset voltage, and an output coupled to the floating voltage source for generating an output voltage. The output voltage exhibits a voltage level that is directly proportional to a duty cycle of the first driving signal.

RELATED APPLICATIONS

This application claims priority to the co-pending provisional patentapplication, Ser. No. 60/797,984, entitled “BUCK TOPOLOGY ALLOWINGSTEP-UP AND POLARITY CHANGE,” with filing date May 5, 2006, and assignedto the assignee of the present invention, which is herein incorporatedby reference in its entirety.

TECHNICAL FIELD

This invention relates to a converter, and more particularly to a bucktopology converter that provides voltage step-up or polarity change.

BACKGROUND ART

PRIOR ART FIG. 1A shows a circuit diagram of a conventionalnon-synchronous boost converter. The conventional non-synchronous boostconverter includes an inductor 110, a switch 102, that is controlled bya pulse width modulation signal 120, a diode 106, and a capacitor 108.

PRIOR ART FIG. 1B shows signal waveforms of signals associated with theconventional non-synchronous boost converter shown in PRIOR ART FIG. 1A.PRIOR ART FIG. 1B shows the waveform 120′ of the pulse width modulationsignal 120, the waveform 130′ of the voltage at node 130, the waveform180′ of the output voltage 180, the waveform 110′ of the current throughinductor 110, waveform 102′ of the current through switch 102, and thewaveform 106′ of the current through diode 106. Furthermore, waveform190′ represents the current through a load coupled to the output 180(not shown), and waveform 192′ represents the ratio of the load currentto the duty cycle of the pulse width modulation signal 120.

As shown in FIG. 1B, the current through the switch 102 (shown as thewaveform 102′) can be much higher than the load current (shown as thewaveform 190′). In addition, in the FIG. 1B circuit, the current throughthe switch 102 depends on the duty cycle of the pulse width modulationsignal 120. Accordingly, such conventional boost converters need aswitch that is suitable for high current/heavy load applications. Suchboost converters encounter stability problems when they operate incontinuous conduction mode (CCM).

FIG. 2A shows a circuit diagram of a conventional buck-boost invertingconverter. The conventional buck-boost converter includes an inductor110, a switch 104 controlled by a pulse width modulation signal 120, adiode 106, and a capacitor 108.

FIG. 2B shows signal waveforms of signals associated with theconventional non-synchronous buck boost inverting converter shown inFIG. 2A. FIG. 2B shows the waveform 120′ of the pulse width modulationsignal 120, the waveform 130′ of the voltage at node 130, the waveform180′ of the output voltage 180, the waveform 110′ of the current throughinductor 110, waveform 104′ of the current through switch 104, and thewaveform 106′ of the current through diode 10,6. Referring to FIG. 2B,waveform 190′ represents the current through a load coupled to theoutput 180 (not shown), and waveform 192′ represents the ratio of theload current to the duty cycle of the pulse width modulation signal 120.

Similarly, as shown in FIG. 2B, the current through the switch 104(shown as the waveform 104′) is much higher than the load current ( bywaveform 190′). The current through the switch 104 depends on the dutycycle of the pulse width modulation signal 120. Accordingly, suchconventional boost converters need a switch suitable for highcurrent/power applications.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a converterincludes an input for receiving an input voltage, a switching circuitcoupled to the input for receiving a first driving signal, a floatingvoltage source coupled to the switching circuit for producing an offsetvoltage, and an output coupled to the floating voltage source forgenerating an output voltage. The output is coupled to the floatingvoltage source via a filter. The output voltage exhibits a voltage levelthat is directly proportional to a duty cycle of the first drivingsignal.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the claimed subject matterwill become apparent as the following Detailed Description proceeds, andupon reference to the Drawings, wherein like numerals depict like parts,and in which:

PRIOR ART FIG. 1A shows a circuit diagram of a conventionalnon-synchronous boost converter, in accordance with the prior art.

PRIOR ART FIG. 1B shows signal waveforms of signals associated with theconventional non-synchronous boost converter in PRIOR ART FIG. 1A, inaccordance with the prior art.

PRIOR ART FIG. 2A shows a circuit diagram of a conventional buck-boostconverter, in accordance with the prior art.

PRIOR ART FIG. 2B shows signal waveforms of signals associated with theconventional non-synchronous boost converter in PRIOR ART FIG. 2A, inaccordance with the prior art.

FIG. 3A shows a circuit diagram of a voltage booster, in accordance withone embodiment of the present invention.

FIG. 3B shows the signal waveforms of signals associated with thevoltage booster in FIG. 3A, in accordance with one embodiment of thepresent invention.

FIG. 4A shows a circuit diagram of a voltage booster, in accordance withone embodiment of the present invention.

FIG. 4B shows a circuit diagram of a voltage booster, in accordance withone embodiment of the present invention.

FIG. 4C shows the signal waveforms of signals associated with thevoltage boosters in FIG. 4A and FIG. 4B, in accordance with oneembodiment of the present invention.

FIG. 5A shows a circuit diagram of a polarity changer, in accordancewith one embodiment of the present invention.

FIG. 5B shows the signal waveforms of signals associated with thepolarity changer in FIG. 5A, in accordance with one embodiment of thepresent invention.

FIG. 6A shows a circuit diagram of a polarity changer, in accordancewith one embodiment of the present invention.

FIG. 6B shows a circuit diagram of a polarity changer, in accordancewith one embodiment of the present invention.

FIG. 6C shows the signal waveforms of signals associated with thepolarity changers in FIG. 6A and FIG. 6B, in accordance with oneembodiment of the present invention.

FIG. 7 shows a flowchart of operations performed by a voltage boosterand/or a polarity changer, in accordance with one embodiment of thepresent invention.

FIG. 8 shows components of an electronic device comprising a voltagebooster or a polarity changer, in accordance with one embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentinvention. While the invention will be described in conjunction with theembodiments, it will be understood that they are not intended to limitthe invention to these embodiments. On the contrary, the invention isintended to cover alternatives, modifications and equivalents, which maybe included within the spirit and scope of the invention as defined bythe appended claims.

Furthermore, in the following detailed description of the presentinvention, numerous specific details are set forth in order to provide athorough understanding of the present invention. However, it will berecognized by one of ordinary skill in the art that the presentinvention may be practiced without these specific details. In otherinstances, well known methods, procedures, components, and circuits havenot been described in detail as not to unnecessarily obscure aspects ofthe present invention.

FIG. 3A shows a circuit diagram of a voltage booster 300, in accordancewith one embodiment of the present invention. The voltage booster 300utilizes a modified buck topology with a floating voltage source toprovide an output voltage that is higher than the input voltage. Thestability issue encountered by conventional boost converters duringcontinuous mode can be avoided, in one embodiment.

The voltage booster 300 comprises an input 370 for receiving an inputvoltage V_in, a switching circuit 303 coupled to the input 370 forreceiving a first driving signal 364 and a second driving signal 362, afloating voltage source (shown as a capacitor 308) coupled to theswitching circuit 303 for producing an offset voltage, and an outputterminal 380 coupled to the floating voltage source (shown as thecapacitor 308) for generating an output voltage V_out. The outputterminal 380 is coupled to the floating voltage source 308 via a filter,in one embodiment. In one embodiment, the output voltage V_out isgreater than the input voltage V_in.

Advantageously, the output voltage V_out comprises a voltage level thatis directly proportional to a duty cycle of the first driving signal364. The output voltage V_out also comprises a positive offset voltageprovided by the capacitor 308, in one embodiment.

In one embodiment, the switching circuit 303 shown as a half bridgecircuit comprises a high side switch 304 controlled by the first drivingsignal 364 and a low side switch 302 controlled by the second drivingsignal 362. The high side switch 304-and the low side switch 302 arecoupled in series. The high side switch 304 is coupled to the input 370and the low side switch 302 is coupled to ground. The switching circuit303 can include different configurations with numerous modifications, inone embodiment. The high side switch 304 and the low side switch 302 areswitched on alternately, in one embodiment.

The voltage booster 300 further comprises a switch shown as a diode 306coupled to the floating source 308 for selectively coupling the floatingsource 308 to the input 370. As such, the offset voltage provided by thefloating source 308 comprises a positive offset voltage V_in, in oneembodiment.

In one embodiment, the voltage booster also comprises a LC filter shownas an inductor 310 and a capacitor 312 for smoothing the output voltageV_out.

In operation, the voltage booster 300 receives the input voltage V_in,receives the first driving signal 364, produces an offset voltage by thefloating voltage source 308, and generates an output voltage V_out. Theoutput voltage V_out comprises a voltage level that is directlyproportional to the duty cycle of the first driving signal 364.

More specifically, the switching circuit 303 (shown as the half bridgecircuit) receives a first driving signal 364 and a second driving signal362. In one embodiment, the first driving signal 364 and the seconddriving signal 362 are pulse width modulation signals. The first drivingsignal 364 and the second driving signal 362 are configured toalternately switch on the high side switch 304 and the low side switch302. As such, the node 330 is coupled to the input and groundalternately.

Advantageously, node 340 is coupled to the input 370 via a diode 306.The capacitor 308 is selectively coupled to the input 370 by the diode306. In other words, the capacitor 308 is charged by the input voltageV_in via the diode 306. As such, the capacitor 308 coupled between node330 and node 340 acts as a floating voltage source which provides anoffset voltage. In one embodiment, the offset voltage provided by thecapacitor 308 comprises positive offset voltage V_in. The capacitor 308(floating voltage source) can provide any level of offset voltagebetween zero and V_in, in one embodiment.

The filter shown as the inductor 310 and the capacitor 312 smoothes thevoltage at node 340 and provides the output voltage V_out at the outputterminal 380, in one embodiment. The output voltage at terminal 380 isgiven by V_out=V_in*d+V_in, where d represents the positive duty cycleof the first driving signal 364.

FIG. 3B shows the signal waveforms of signals associated with thevoltage booster 300 in FIG. 3A, in accordance with one embodiment of thepresent invention. FIG. 3B will be described in combination with FIG.3A.

Waveform 330′ represents the voltage at node 330. Waveform 364′represents the voltage of the first driving signal 364. VDDP representsamplitude of the driving signal of the high side switch 304. Waveform340′ represents the voltage at node 340. By comparing waveform 330′ andwaveform 340′, the voltage at node 340 (waveform 340′) is equal to thevoltage at node 330 (waveform 330′) shifted by a positive offset voltageV_in, in one embodiment.

Waveform 380′ represents the output voltage V_out at output terminal380. As described above, the output voltage V_out is given by:V_out=V_in*d+V_in=V_in(1+d), where d represents the positive duty cycleof the first driving signal 364 (0<=d<=1). Therefore, the output voltageV_out comprises a voltage level that is directly proportional to theduty cycle d of the first driving signal 364. In addition, the outputvoltage V_out comprises a positive offset voltage V_in provided by thefloating voltage source 308.

Waveform 310′ represents the current through the inductor 310. Waveform390′ (load current) represents the current through a load (not shown inFIG. 3A) coupled to the output terminal 380. Waveform 304′ representsthe current through the high side switch 304. Waveform 302′ representsthe current through the low side switch 302. Waveform 306′ representsthe current through the diode 306.

Advantageously, the current through the switches (e.g., the low sideswitch 302 and the diode 306) is lower (equal to the load current plus aripple current) compared to the prior art.

FIG. 4A shows a circuit diagram of a voltage booster 400, in accordancewith one embodiment of the present invention. Elements that are labeledthe same as in FIG. 3A have similar functions and will not berepetitively described herein for purposes of brevity and clarity. Thevoltage booster 400 utilizes a modified buck topology with a floatingvoltage source to provide an output voltage that is higher than theinput voltage. The stability issue encountered by conventional boostconverters during continuous mode can be avoided, in one embodiment.

As shown in FIG. 4A, a switch shown as a MOSFET 402 is coupled to thefloating source 308 for selectively coupling the floating source 308 tothe input 370. As such, the offset voltage provided by the floatingsource 308 comprises a positive offset voltage V_in.

The switch 402 is controlled by a pulse width modulation control signal366. In one embodiment, the control signal 366 and the first drivingsignal 364 are configured to switch on the high side switch 304 and thecontrol switch 402 alternately. As such, the switch 402 and the low sideswitch 302 are switched on simultaneously, in one embodiment.

Advantageously, the MOSFET 402 can reduce conduction loss, in oneembodiment. The operation of the voltage booster 400 is similar to theoperation of the voltage booster 300 in FIG. 3A. Hence, the detailedoperation of the voltage booster 400 will not be described herein forpurposes of clarity and brevity.

Similarly, the output voltage V_out is obtained by:V_out=V_in(1+d)=V_in*d+V_in, where d represents the positive duty cycleof the first driving signal 364. Therefore, the output voltage comprisesa voltage level that is directly proportional to the duty cycle d of thefirst driving signal 364. In addition, the output voltage V_outcomprises a positive offset voltage V_in provided by the floatingvoltage source 308.

FIG. 4B shows a circuit diagram of a voltage booster 400′, in accordancewith one embodiment of the present invention. Elements that are labeledthe same as in FIG. 3A and FIG. 4A have similar functions and will notbe repetitively described herein for purposes of brevity and clarity.The voltage booster 400′ utilizes a modified buck topology with afloating voltage source to provide an output voltage that is higher thanthe input voltage. The stability issue encountered by conventional boostconverters during continuous mode can be avoided, in one embodiment.

FIG. 4B provides a simplified control topology (level shifter) for thecontrol switch 402. As shown in FIG. 4B, the gate terminal 360 of thecontrol switch 402 is coupled to the second driving signal 362 via acapacitor 408 and is coupled to the input terminal 370 via a diode 406.As such, the level of the control signal 366′ for the switch 402 isequal to the level of the second driving signal shifted by a positiveoffset voltage V-in, in one embodiment.

The high side switch 304 and the low side switch 302 are switched onalternately, in one embodiment. The low side switch 302 and the switch402 are switched on simultaneously, in one embodiment.

The operation of the voltage booster 400′ is similar to the operation ofthe voltage booster 300 in FIG. 3A and the voltage booster 400 in FIG.4A. Hence, the detailed operation of the voltage booster 400′ will notbe described herein for purposes of clarity and brevity.

Similarly, the output voltage V_out is obtained by:V_out=V_in(1+d)=V_in*d+V_in, where d represents the positive duty cycleof the first driving signal 364. Therefore, the output voltage comprisesa voltage level that is directly proportional to the duty cycle d of thefirst driving signal 364. In addition, the output voltage V_outcomprises a positive offset voltage V_in provided by the floatingvoltage source 308.

FIG. 4C shows the signal waveforms of signals associated with thevoltage booster 400 and the voltage booster 400′, in accordance with oneembodiment of the present invention.

As shown in FIG. 4C, waveform 330′ represents the voltage at node 330.Waveform 364′ represents the voltage of the first driving signal 364.VDDP represents the amplitude of the driving signal of the high sideswitch 304. Waveform 362′ represents the voltage of the second drivingsignal 362. Waveform 340′ represents the voltage at node 340. Bycomparing waveform 330′ and waveform 340′, the voltage at node 340(waveform 340′) is equal to the voltage at node 330 (waveform 330′)shifted by a positive offset voltage V in, in one embodiment.

Waveform 366′ represents the voltage at node 360. As described above,the voltage at node 360 (waveform 366′) is equal to the voltage of thesecond driving signal 362 shifted by a positive offset voltage which isV_in, in one embodiment. Waveform 380′ represents the voltage at theoutput terminal 380. As described above, the output voltage V_out isobtained by: V_out=V_in(1+d)=V_in*d+V_in, where d represents thepositive duty cycle of the first driving signal 364. Therefore, theoutput voltage comprises a voltage level that is directly proportionalto the duty cycle d of the first driving signal 364. In addition, theoutput voltage V_out comprises a positive offset voltage V_in providedby the floating voltage source 308.

Accordingly, voltage boosters in accordance with the embodimentsprovided in FIG. 3A, FIG. 4A, and FIG. 4B comprise an output voltageV_out that is directly proportional to the duty cycle of the firstdriving signal. A regular buck converter controller can be used to drivethe voltage boosters in accordance with the present invention, in oneembodiment. Other kinds of DC/DC controllers can also be used to drivethe voltage boosters in accordance with the present invention, in oneembodiment. The controller is used to control the switching circuit.More specifically, the controller is used to generate the first drivingsignal and the second driving signal. A feedback circuit (e.g., avoltage divider) can be coupled to the output to provide a feedbacksignal, in one embodiment. In such an embodiment, the feed back signalcan be compared with a reference signal to adjust the output voltage.

Advantageously, voltage boosters in accordance with the embodimentsprovided in FIG. 3A, FIG. 4A, and FIG. 4B utilize a modified bucktopology with a floating voltage source to provide an output voltagethat is higher than the input voltage. Therefore, the stability issueencountered by conventional boost converters during continuous mode canbe avoided, in one embodiment.

Furthermore, the current flowing through the switches of voltageboosters in accordance with the embodiments provided in FIG. 3A, FIG.4A, and FIG. 4B is lower compared to the prior art. As such, voltageboosters in accordance with the present invention have high efficiencyand are suitable for high current and/or heavy load applications.

FIG. 5A shows a circuit diagram of a polarity changer 500, in accordancewith one embodiment of the present invention. The polarity changer 500utilizes a modified buck topology with a floating voltage source toprovide an output voltage. The polarity of the output voltage isopposite to the polarity of the input voltage. The stability issueencountered by conventional boost converters during continuous mode canbe avoided, in one embodiment.

The polarity changer 500 comprises an input 570 receiving an inputvoltage V_in, a switching circuit 503 coupled to the input 570 forreceiving a first driving signal 564 and a second driving signal 562, afloating voltage source (shown as a capacitor 508) coupled to theswitching circuit 503 for producing an offset voltage, and an outputterminal 580 coupled to the floating voltage source (shown as thecapacitor 508) for generating an output voltage V_out. The outputterminal 580 is coupled to the floating voltage source 508 via a filter.The polarity of the output voltage V_out is opposite to the polarity ofthe input voltage V_in.

Advantageously, the output voltage comprises a voltage level that isdirectly proportional to a duty cycle of the first driving signal 564.The output voltage also comprises an offset voltage provided by thecapacitor 508, in one embodiment.

In one embodiment, the switching circuit 503 shown as a half bridgecircuit comprises a high side switch 504 controlled by the first drivingsignal 564 and a low side switch 502 controlled by the second drivingsignal 562. The high side switch 504 and the low side switch 502 arecoupled in series. The high side switch 504 is coupled to the input 570and the low side switch 502 is coupled to ground. The switching circuit503 can include different configurations with numerous modifications.The first driving signal 564 and the second driving signal 562 areconfigured to switch on the high side switch 504 and the low side switch502 alternately, in one embodiment.

The voltage booster 500 further comprises a switch shown as a diode 506coupled to the floating source 508 for selectively coupling the floatingsource 508 to ground. As such, the offset voltage provided by thefloating source 508 comprises a negative offset voltage—V_in, in oneembodiment.

In one embodiment, the voltage booster also comprises a filter shown asan inductor 510 and a capacitor 512 for smoothing the output voltageV_out.

In operation, the voltage booster 500 receives the input voltage V_in,receives the first driving signal 564, produces an offset voltage by thefloating voltage source 508 and generates an output voltage V_out. Theoutput voltage V_out comprises a voltage level that is directlyproportional to the duty cycle of the first driving signal 564.

More specifically, the switching circuit 503 (shown as the half bridgecircuit) receives a first driving signal 564 and a second driving signal562. In one embodiment, the first driving signal 564 and the seconddriving signal 562 are pulse width modulation signals. The first drivingsignal 564 and the second driving signal 562 are configured to switch onthe high side switch 504 and the low side switch alternately, in oneembodiment. As such, by alternately conducting the high side switch 504and the low side switch 502, the node 530 is coupled to the input andground in an alternating fashion.

Advantageously, node 540 is coupled to ground via a diode 506. Thecapacitor 508 is selectively coupled to ground by the diode 506. Assuch, the capacitor 508 coupled between node 530 and node 540 acts as afloating voltage source which provides an offset voltage. In oneembodiment, the offset voltage provided by the capacitor 508 comprises anegative offset voltage −V_in. The capacitor 508 (floating voltagesource) can provide any level of offset voltage between −V_in and zero,in one embodiment.

The filter shown as the inductor 510 and the capacitor 512 smoothes thevoltage at node 540 and provides the output voltage V_out at the outputterminal 580, in one embodiment. The output voltage at terminal 580 isgiven by V_out=V_in*d_V_in, where d represents the positive duty cycleof the first driving signal 564.

FIG. 5B shows the signal waveforms of signals associated with thepolarity changer 500 in FIG. 5A, in accordance with one embodiment ofthe present invention. FIG. 5B will be described in combination withFIG. 5A.

Waveform 530′ represents the voltage at node 530. Waveform 564′represents the voltage of the first driving signal 564. VDDP representsthe amplitude of the driving signal of the high side switch 504.Waveform 562′ represents the voltage of the second driving signal 562.Waveform 540′ represents the voltage at node 540. By comparing waveform530′ and waveform 540′, the voltage at node 540 (waveform 540′) is equalto the voltage at node 530 (waveform 530′) shifted by a negative offsetvoltage −V_in, in one embodiment.

Waveform 580′ represents the output voltage V_out at output terminal580. As described above, the output voltage V_out is given by:V_out=V_in*d−V_in=V_in(d−1), where d represents the positive duty cycleof the first driving signal 564. Therefore, the output voltage V_outcomprises a voltage level that is directly proportional to the dutycycle d of the first driving signal 564. In addition, the output voltageV_out comprises a negative offset voltage −V_in provided by the floatingvoltage source 508.

Waveform 510′ represents the current through the inductor 510. Waveform590′ (load current) represents the current through a load (not shown inFIG. 5A) coupled to the output terminal 580. Waveform 504′ representsthe current through the high side switch 504. Waveform 502′ representsthe current through the low side switch 502. Waveform 506′ representsthe current through the diode 506.

Advantageously, the current through the switches (e.g., the high sideswitch 504 and the diode 506) is lower (equal to the load current plusthe ripple current) compared to the prior art.

FIG. 6A shows a circuit diagram of a polarity changer 600, in accordancewith one embodiment of the present invention. Elements that are labeledthe same as in FIG. 5A have similar functions and will not berepetitively described herein for purposes of brevity and clarity. Thepolarity changer 600 utilizes a modified buck topology with a floatingvoltage source to provide an output voltage. The polarity of the outputvoltage is opposite to the polarity of the input voltage. The stabilityissue encountered by conventional boost converters during continuousmode can be avoided, in one embodiment.

As shown in FIG. 6A, a control switch shown as a MOSFET 602 is coupledto the floating source 508 for selectively coupling the floating source508 to the input 570. As such, the offset voltage provided by thefloating source 508 comprises a negative offset voltage V_in.

The control switch 602 is controlled by a pulse width modulation controlsignal 666. In one embodiment, the control signal 666 and the firstdriving signal 564 are configured to switch on the control switch 602and the high side switch 504 simultaneously. As such, the switch 602 andthe low side switch 562 are switched on simultaneously, in oneembodiment.

Advantageously, the control switch shown as the MOSFET 602 can reduceconduction loss, in one embodiment. The operation of the polaritychanger 600 is similar to the operation of the polarity changer 500 inFIG. 5A. Hence, the detailed operation of the polarity changer 600 willnot be described herein for purposes of clarity and brevity.

Similarly, the output voltage V_out is obtained by:V_out=V_in(d−1)=V_in*d−V_in, where d represents the positive duty cycleof the first driving signal 564. Therefore, the output voltage comprisesa voltage level that is directly proportional to the duty cycle d of thefirst driving signal 564. In addition, the output voltage V_outcomprises a negative offset voltage −V_in provided by the floatingvoltage source 508.

FIG. 6B shows a circuit diagram of a polarity changer 600′, inaccordance with one embodiment of the present invention. Elements thatare labeled the same as in FIG. 5A and FIG. 6A have similar functionsand will not be repetitively described herein for purposes of brevityand clarity. The polarity changer 600′ utilizes a modified buck topologywith a floating voltage source to provide an output voltage. Thepolarity of the output voltage is opposite to the polarity of the inputvoltage. The stability issue encountered by conventional boostconverters during continuous mode can be avoided, in one embodiment.

FIG. 6B provides a simplified control topology (level shifter) for thecontrol switch 602. As shown in FIG. 6B, the gate terminal 660 of theswitch 602 is coupled to the first driving signal 564 via a capacitor608 and is coupled to ground via a diode 606. As such, the controlsignal 666′ for switching the switch 602 is equal to the first drivingsignal 564 shifted by a negative offset voltage −V_in, in oneembodiment.

Similarly, the high side switch 504 and the low side switch 502 areswitched on alternately. The high side switch 504 and the control switch602 are switched on simultaneously, in one embodiment.

The operation of the polarity changer 600′ is similar to the operationof the polarity changer 500 in FIG. SA and the polarity changer 600 inFIG. 6A. Hence, the detailed operation of the polarity changer 600′ willnot be described herein for purposes of clarity and brevity.

Similarly, the output voltage V-out is obtained by:V_out=V_in(d−1)=V_in*d−V_in, where d represents the positive duty cycleof the first driving signal 564. Therefore, the output voltage comprisesa voltage level that is directly proportional to the duty cycle d of thefirst driving signal 564. In addition, the output voltage V_outcomprises a negative offset voltage −V_in provided by the floatingvoltage source 508.

FIG. 6C shows the signal waveforms of signals associated with thepolarity changer 600 and the polarity changer 600′, in accordance withone embodiment of the present invention.

As shown in FIG. 6C, waveform 530′ represents the voltage at node 530.Waveform 564′ represents the voltage of the first driving signal 564.VDDP represents the amplitude of the driving signal of the high sideswitch 504. Waveform 562′ represents the voltage of the second drivingsignal 562. Waveform 540′ represents the voltage at node 540. Bycomparing waveform 530′ and waveform 540′, the voltage at node 540(waveform 540′) is equal to the voltage at node 530 (waveform 530′)shifted by a negative offset voltage −V_in, in one embodiment.

Waveform 666′ represents the voltage at node 660. As described above,the voltage at node 660 (waveform 666′) is equal to the voltage of thefirst driving signal 564 shifted by a negative offset voltage which is−V_in, in one embodiment. Waveform 580′ represents the voltage at theoutput terminal 580. As described above, the output voltage V_out isobtained by: V_out=V_in(d−1)=V_in*d−V_in, where d represents thepositive duty cycle of the first driving signal 564. Therefore, theoutput voltage comprises a voltage level that is directly proportionalto the duty cycle d of the first driving signal 564. In addition, theoutput voltage V_out comprises a negative offset voltage −V_in providedby the floating voltage source 508.

Accordingly, polarity changers in accordance with the embodimentsprovided in FIG. 5A, FIG. 6A, and FIG. 6B comprise an output voltageV_out that is directly proportional to the duty cycle of the firstdriving signal. A modified buck converter controller can be used todrive the polarity changers in accordance with the present invention, inone embodiment. Other kinds of DC/DC controllers can also be used todrive the polarity changers in accordance with the present invention, inone embodiment. The controller is used to control the switching circuit.More specifically, the controller is used to generate the first drivingsignal and the second driving signal. A feedback circuit (e.g., avoltage divider) can be coupled to the output to provide a feedbacksignal, in one embodiment. In such an embodiment, the feed back signalcan be compared with a reference signal to adjust the output voltage.

Advantageously, polarity changers in accordance with the embodimentsprovided in FIG. 3A, FIG. 4A, and FIG. 4B utilize a modified bucktopology with a floating voltage source to provide an output voltagethat has an opposite polarity of the input voltage.

Furthermore, the current flowing through the switches of polaritychangers in accordance with the embodiments provided in FIG. 3A, FIG.4A, and FIG. 4B is lower compared to the prior art. As such, polaritychangers in accordance with the present invention have high efficiencyand are suitable for high current and/or heavy load applications.

FIG. 7 shows a flowchart 700 of the operations performed by a voltagebooster such as is described with reference to FIG. 3A-FIG. 4C and/or apolarity changer such as is described with reference to FIG. 5A-FIG. 6C,in accordance with one embodiment of the present invention.

As shown in FIG. 7, an input voltage is received in block 701. In block702, a first driving signal is received. In one embodiment, the firstdriving signal is a pulse width modulation signal having a duty cycle d.In block 703, a floating voltage source is selectively coupled to theinput or ground. More specifically, when a voltage booster such as isdiscussed with reference to FIG. 3A-FIG. 4C is implemented, the floatingvoltage source is selectively coupled to the input. However, when apolarity changer such as is discussed with reference to FIG. 5A-FIG. 6Cis implemented, the floating voltage source is selectively coupled toground.

In block 704, an offset voltage is generated by the floating voltagesource. More specifically, if the floating voltage source is selectivelycoupled to the input, the floating voltage source provides a positiveoffset voltage V_in. If the floating voltage source is selectivelycoupled to ground, the floating voltage source provides a negativeoffset voltage −V_in.

In block 705, an output voltage is generated. In block 706, the outputvoltage is smoothed by a filter comprising an inductor and a capacitor.Advantageously, this output voltage has a voltage level that is directlyproportional to the duty cycle d of the first driving signal.

FIG. 8 shows components of an electronic device 800 that includes avoltage booster or a polarity changer, in accordance with one embodimentof the present invention. The electronic device may include, but is notlimited to, a desktop computer, a laptop computer, and a personaldigital device, etc.

As shown in FIG. 8, the components of an electronic device 800 include aconverter 820, a controller 810, and load terminals 890A and 890B. Inthe electronic device 800, the converter 820 is controlled by thecontroller 810 and converts an input signal at the input 870 to anoutput signal at the converter output 880 for powering a load 840. Inone embodiment, the converter 820 can include a voltage booster asdiscussed with reference to FIG. 3A-FIG. 4C. In another embodiment, theconverter 820 can include a polarity changer as discussed with referenceto FIG. 5A-FIG. 6C. The voltage booster and the polarity changer aredescribed in detail above. Hence, a repetitive description will beomitted herein for purposes of brevity and clarity.

The converter 820 comprises an input 870 that receives an input voltage,a switching circuit 803 coupled to the input 870 for receiving a firstdriving signal 864 having a duty cycle; a floating voltage source 808coupled to the switching circuit 803 for producing an offset voltage,and a converter output 880 coupled to the floating voltage source 808for generating an output voltage. The converter output 880 is coupled tothe floating voltage source 808 via a filter 814, in one embodiment.Advantageously, the output voltage has a voltage level that is directlyproportional to the duty cycle of the first driving signal 864.

The controller 810 is coupled to the switching circuit 803 for providingthe first driving signal 864 to the switching circuit 803. In oneembodiment, the first driving signal 864 is a pulse width modulationsignal having a duty cycle d.

The converter output 880 is coupled to the load terminal 890A forproviding an output voltage to a load 840. As such, in an electronicdevice, the converter 820 is controlled by the controller 810 andconverts an input signal at the input 870 to an output signal at theconverter output 880 for powering the load 840.

While the foregoing description and drawings represent the preferredembodiments of the present invention, it will be understood that variousadditions, modifications and substitutions may be made therein withoutdeparting from the spirit and scope of the principles of the presentinvention as defined in the accompanying claims. One skilled in the artwill appreciate that the invention may be used with many modificationsof form, structure, arrangement, proportions, materials, elements, andcomponents and otherwise, used in the practice of the invention, whichare particularly adapted to specific environments and operativerequirements without departing from the principles of the presentinvention. The presently disclosed embodiments are therefore to beconsidered in all respects as illustrative and not restrictive, thescope of the invention being indicated by the appended claims and theirlegal equivalents, and not limited to the foregoing description.

1. A converter comprising: an input for receiving an input voltage; a switching circuit coupled to said input for receiving a first driving signal, wherein said first driving signal has a duty cycle; a floating voltage source coupled to said switching circuit for producing an offset voltage; and an output coupled to said floating voltage source for generating an output voltage, wherein said output voltage has a voltage level that is directly proportional to said duty cycle.
 2. The converter as claimed in claim 1, wherein said output voltage comprises said offset voltage.
 3. The converter as claimed in claim 1, wherein said floating voltage source comprises a capacitor.
 4. The converter as claimed in claim 2, further comprising a control switch coupled to said floating voltage source for selectively coupling said floating source to said input.
 5. The converter as claimed in claim 2, further comprising a control switch coupled to said floating voltage source for selectively coupling said floating source to ground.
 6. The converter as claimed in claim 4, wherein said offset voltage comprises a positive value of said input voltage.
 7. The converter as claimed in claim 5, wherein said offset voltage comprises a negative value of said input voltage.
 8. The converter as claimed in claim 4, wherein said control switch and a switch controlled by said first driving signal are switched on alternately.
 9. The converter as claimed in claim 5, wherein said control switch and a switch controlled by said first driving signal are switched on simultaneously.
 10. The converter as claimed in claim 4, wherein said output voltage is greater than said input voltage.
 11. The converter as claimed in claim 5, wherein a polarity of said output voltage is opposite to a polarity of said input voltage.
 12. The converter as claimed in claim 1, wherein said switching circuit comprises a half bridge circuit.
 13. The converter as claimed in claim 1, further comprising a filter coupled to said floating voltage source for smoothing said output voltage.
 14. The converter as claimed in claim 13, wherein said filter comprises an inductor.
 15. The converter as claimed in claim 13, wherein said filter comprises a capacitor.
 16. A method for converting a signal comprising: receiving an input voltage; receiving a first driving signal, wherein said first driving signal has a duty cycle; producing an offset voltage; and generating an output voltage, wherein said output voltage comprises a voltage level that is directly proportional to said duty cycle.
 17. The method as claimed in claim 16, further comprising selectively coupling a floating source to an input.
 18. The method as claimed in claim 16, further comprising selectively coupling a floating source to ground.
 19. The method as claimed in claim 16, further comprising smoothing said output voltage.
 20. An electronic device comprising: a converter comprising: an input receiving an input voltage; a switching circuit coupled to said input for receiving a first driving signal, wherein said first driving signal has a duty cycle; a floating voltage source coupled to said switching circuit for producing an offset voltage; and a converter output coupled to said floating voltage source for generating an output voltage, wherein said output voltage comprises a voltage level that is directly proportional to said duty cycle; a controller coupled to said switching circuit for generating said first driving signal; and load terminals for providing an output to a load. 